Ignition system



July 5, 1966 Original Filed Dec. 30

7'0 STAR TEA w a .2 m? .MM 5 M QFM My KX m L E M V.- B m R m 5 m A TTORNEVS 3,259,798 IGNITEGN SYSTEM Elmer E. Yonge, Manchester, Mich, assignor to Ford Motor Company, Dearborn, Micln, a corporation of Delaware Continuation of application Ser. No. 862,883, Dec. 30, 1959. This application Mar. 18, 1963, Ser. No. 266,468

12 Claims. (Cl. 315-209) This application is a continuation of my copending application Serial Number 862,883, filed December 30, 1959, now abandoned.

This invention relates to an ignition system for an internal combustion engine, and more particularly to a transistorized ignition system for an internal combustion engine.

In conventional internal combustion engine ignition systems, full battery voltage is applied across the primary winding of the ignition coil through a set of distributor breaker points. As a result, a heavy current flows in the primary winding and through the contact points. When the contact points are opened, arcing occurs across the points since current through the primary winding continues to flow because of the collapsing magnetic field of the ignition coil. This causes pitting and corrosion of the breaker points, and experience shows that the breaker points have to be periodically replaced because of this pitting and corrosion.

The present invention provides an ignition system in which pitting and corrosion of the breaker points are substantially reduced. This is accomplished by employing a transistor circuit in which the primary of an ignition coil is positioned in the load circuit of the transistor, and in which a pair of distributor breaker points are positioned in the base or control circuit of the transistor to alternately turn the transistor on and off. Thus the breaker points switch only base or control circuit current which is substantially less than the primary current that must be switched by conventional ignition systems.

It is Well known that the voltage induced in the secondary winding of an ignition coil is proportional to the time rate of change of the flux in the coil, and that peak outputs occur when the magnetic field in the coil collapses due to change in primary current as the switching means in the primary circuit is opened. It follows, therefore, that high secondary winding outputs will occur if short switching times for the primary current can be employed. The present invention provides a circuit for reducing switching time in transistorized ignition systems by applying a pulse of electrical energy to the base of the transistor when the distributor breaker points are opened. This pulse of electrical energy has a polarity opposite to that of the bias voltage applied to the base to cause transistor conduction. This pulse of electrical energy thus causes the transistor to be cut off very rapidly and as a result high secondary output voltages are obtained.

The pulse of electrical energy applied to the base also permits the transistor to be operated at peak voltages in excess of the absolute maximum rating of the collector to emitter voltage with the emitter common to the base. This pulse of electrical energy of opposite polarity to the normal bias voltage applied to the base of the transistor when the distributor breaker points are opened, therefore, permits the primary winding of the ignition coil to be operated at higher peak voltages than would otherwise be possible. As a result, higher peak secondary output voltages are obtained.

An object of the present invention is the provision of an ignition system for an internal combustion engine in which the breaker points have a long life.

Another object of the invention is the provision of a transistorized ignition system for an internal combustion United States Patent ice engine in which the transistor is cut ofif very rapidly when it is desired to interrupt the current in the primary winding of an ignition coil.

, A further object of the invention is to provide a transistorized ignition system for an internal combustion engine in which the transistor and the primary winding of an ignition coil may be operated at higher peak voltages than have heretofore been obtained with comparable components.

Other objects and attendant advantages of the present invention will become more readily apparent as the specification is considered in connection with the accompanying drawings in which FIG. 1 is a circuit diagram of one embodiment of the invention;

FIG. 2 is a circuit diagram of another embodiment of the invention, and

FIG. 3 is a circuit diagram of still another embodiment of the invention.

Referring now to the drawings in which like reference numerals designate like parts throughout the several views thereof, there is shown in FIG. 1 a transistorized ignition system which may be used in an automobile vehicle employing a battery having a negative ground. A semiconductor device preferably in the form of a transistor generally designated by the numeral 10, is employed. The semiconductor device or transistor has a pair of output electrodes that may take the form of a collector 11 grounded through lead wire 12 and an emitter 13 which is connected to one terminal of the primary winding 14 of ignition coil 15. The control electrode or base 16 of the semiconductor device or transistor is connected to the negative terminal 17 of storage battery 18 through a base current limiting resistor 19 and a current interrupting means that may conveniently take the form of a pair of distributor breaker points 21. The other terminal of the primary winding 14 is connected to the positive terminal 22 of the storage battery 18 through a current limiting resistor 23 and ignition switch 24. The external circuit connecting the emitter 13 with the control electrode or base 16 may be defined as a control circuit, while the external circuit connecting the emitter 13 with the collector 11 may be defined as a load circuit.

Provision is made for shorting out part of the current limiting resistor 23 during engine starting. This is accomplished by center tapping the resistor 23 with a lead 25 which is connected to the armature 26 of starter switch relay 27. The ignition switch 24 has 'a Start position 28 and an On position 29. When the ignition switch is positioned in the Start position against terminal 28, the relay solenoid 30 moves armature 26 into contact with contacts 31 and 32. The positive terminal of the battery 22 is therefore connected to lead 33 through the armature 26 and lead 34. The lead 33 is connected to energize the starting motor of an internal combustion engine with which the transistorized ignition system may be employed. When armature 26 is in contact with points 31 and 32, it can be appreciated that approximately onehalf of limiting resistor 23 is short circuited through lead 34, armature 26 and lead 25. When the engine has started, the ignition switch is returned to the On position, or contact 29, and the Whole of resistor 23 is inserted in series with the primary winding 14. Such an arrangement permits a greater portion of full battery current to flow in the primary winding during engine starting conditions, when it is needed, than during engine running conditions.

The ignition coil 15 includes a secondary winding 35 which has one terminal grounded, and which has the other terminal connected to rotating arm 36 of distributor 37 through lead 38. The rotating arm 36 sequentially connects the secondary winding 35 of the ignition coil to spark plugs 41 through 46 by means of distributor cap contacts 51 through 56 and the spark plug wires 57. The rotating arm 36 and the breaker points 21 of the distributor are operated in timed relationship so that the breaker points are opened when the rotating arm comes into contact with any one of the distributor cap contacts.

Means are provided for applying a pulse of electrical energy to the base of the transistor each time the breaker points 21 are opened. This pulse of electrical energy has a polarity opposite to the bias applied to the transistor to cause conduction thereof. The means employed may conveniently take the form of a feedback winding 61 having one terminal thereof connected to one terminal of the primary winding 14 and the emitter 13, with the other terminal thereof connected to the base 16 of the transistor through limiting resistor 62. A Zener diode 63 having a breakdown voltage substantially equal to the voltage at which the transistor is designed to operate, may be connected across the transistor from collector 11 to emitter 13 to protect the transistor from voltages in excess of those at which it is designed to operate.

In operation of the ignition system shown in FIG. 1, the operator of the automotive vehicle in which it is installed moves the ignition switch 24 to the Start position shown at 28. This applies a positive potential to the emitter 13 of the transistor 10 through approximately one-half of the current limiting resistor 23 and the primary winding 14 of the ignition coil 15. The collector of the transistor is biased negatively with respect to the emitter since it is connected to the negative terminal of the battery 17, and similarly, base 16 is biased negatively with respect to the emitter through the base current limiting resistor 19 and closed distributor breaker points 21.

Electrical energy from the battery 18 is applied to the starting motor through the lead 34, armature 26 and lead 33, as previously described. The transistor Will now conduct and a large amount of current will fiow through the primary winding of the ignition coil 15. As can be readily appreciated from the polarity markings of the primary winding 14 and feedback winding 61, a small negative potential will be applied to the base of the transistor by means of the feedback winding '61 when current is increasing in the primary winding 14. As the starting motor drives the internal combustion engine, the points 21 will open at approximately the time the rotating arm 36 of the distributor makes contact with one of the distributor cap contacts. When this happens, the base bias is removed from the transistor, and the transistor commences to shut off thereby offering an increased resistance to the flow of primary current. duced, a positive pulse of electrical energy is applied to the base of the transistor by the feedback winding 61, since the magnetic field in the ignition coil is collapsing and the rate of change of flux is in the reverse direction from that prevailing when the current in the primary winding is increasing.

The positive pulse applied to the base of the transistor causes a rapid transition from the full-on to the fulloff condition. The collapsing magnetic field of the primary winding 14 induces a high voltage in the secondary winding 35 which is applied to one of the spark plugs through the rotating arm and one of the distributor cap contacts of the distributor. When the primary current has been reduced substantially to zero, the positive pulse applied to the base of the transistor through the feedback winding will disappear. Shortly thereafter, the'breaker points 21 close and a negative bias is again applied to the base of the transistor. The cycle then repeats. After the internal combustion engine has started, the ignition switch 24 is moved from the Stant position to the On position at 29 so that the full value of the resistor 23 is inserted in series with the primary winding.

The Zener diode 63 will protect the transistor from substantial over-voltages which may occur if the secondary winding of the ignition coil suddenly 'has the load As the primary current is reremoved. This may occur if one of the spark plug wires comes loose from a spark plug.

In this instance, the Zener diode 'will provide a very low impedance path across the transistor for emitter to collector voltages in excess of the breakdown voltage of the Zener diode. Since the transistor can be operated at voltages in excess of the absolute maximum rating of emitter to collector voltage with the emitter common to the base because of the pulse of electrical energy applied to the base when the distributor breaker points open, the Zener diode employed may have a breakdown voltage equal to the peak voltage at which the transistor operates. This may be considerably in excess of the absolute maximum rating of the collector to emitter voltage of the transistor with the emitter common to the base.

FIG. 2 shows an embodiment of the invention which is similar to FIG. 1, but discloses the transistorized ignition system in conjunction with a battery which has a positive ground. In this instance, the collector 11 of the transistor 10 is connected to the primary winding 14 of the ignition coil, and the emitter 13 is connected to the positive terminal of the storage battery 18 or ground. In order to provide the proper bias for the base 16 of the transistor, it must be connected to receive a negative potential with respect to the emitter, and this is accomplished by connecting one terminal of the breaker points 21 between the resistor 23 and the primary winding 14. In this embodiment, a positive pulse of electrical energy is also applied to the base of the transistor when the breaker points 21 are opened. This is accomplished by a separate feed-back winding 61 which has one terminal connected to the positive terminal of the battery 18 or ground, and which has the other terminal connected to the base of the transistor through resistor 62' and the current limiting resistor 19. As can readily be appreciated by the polarity markings on the windings of the ignition coil, including the feedback winding, a positive pulse of electrical energy is applied to the control electrode or base 16 when the breaker points 21 are opened.

Another embodiment of the invention is shown in FIG. 3. In this embodiment a dilfused alloy junction type transistor may be employed. In such transistors large voltages applied to the base of the transistor of opposite polarity to the voltage applied to cause transistor conduction may damage the transistor. Therefore, means for limiting this voltage are employed which may take the form of a diode, or a plurality of diodes connected in series, designated by the numerals 71, 72 and 73. The diodes 71, 72 and 73 are positioned between the base 16 and the emitter 13 of the transistor with the polarity shown.

When the positive pulse of electrical energy is applied to the base 16 of. the transistor by the feedback winding 61 as the breaker points 21 are opened, the base will be biased in a positive direction with respect to the emitter. The diodes 71, 72 and 73, limit the amount of the potential difference between the base and the emitter. For example, if ordinary silicon diodes are employed having a forward resistance of approximately .5 of a volt, three of these employed in series will limit the potential difference between the base of the transistor and the emitter to 1 /2 volts. This is sufficient to cause quick switching action by the transistor, and at the same time it prevents the base of the transistor from receiving a positive potential of a magnitude to cause damage to the transistor.

The ignition system shown in FIGS. 1 and 2 may employ the following components which are given by way of example only:

Transistor 1tlany of the following transistors may be employed:

2N-1136B 2N-1031C 2N-174 Primary winding 14-80 turns of No. 19 plain enamel copper wire Secondary winding 35--24,000 turns of No. 40 plain enamel copper wire Feedback windings 61 and 61'3 turns of chromel wire or three turns of No. 24 plain enamel copper wire Resistor 192O ohms Resistors 62 and 62'8 ohms Resistor 23.5 ohm Battery 18a 12 volt automotive vehicle battery Zener diode 6310M100Z The ignition system shown in FIG. 3 may employ the following components which are given by way of example only:

Transistor 2.Nl073-A, a dilfused alloy junction type transistor Primary winding 1480 turns of No. 19 plain enamel copper wire Secondary winding 3524,000 turns of No. 4-0 plain enamel Wire Feedback winding 61-3 turns of chromel wire or 3 turns of No. 24 plain enamel copper wire Resistor 19-20 ohms Resistor 628 ohms Resistor 23.5 ohm Battery 18l2 volt automotive vehicle battery Zener diode 63-10M100Z Diodes 71, 72 and 73-Silicon diode 1N-2069 In connection with feedback windings 61 and 61' and resistors 62 and 62', the resistors 62 and 62 may represent an external resistor or the resistance of the feedback winding itself. In the abope examples, with three turns of chromel wire being employed for the feedback windings the resistors 62 and 62 represent the resistance of the feedback winding itself while with three turns of No. 24 plain enamel copper wire, the resistors 62 and 62' represent separate external resistors.

In all three of the embodiments of the invention, there is provided an ignition system in which breaker point life is substantially increased over conventional ignition systems since the breaker points need only switch the base current of the transistor rather than full primary current. There is also provided a transistorized ignition system which produces large secondary voltages as a result of rapid cutoff of the transistor when the breaker points are opened. This system may also be operated with peak primary winding voltages in excess of those previously obtained with comparable components.

Although the invention is shown employing PNP type transistors the invention is in no way limited to this type of transistor. It will be readily apparent to those skilled in the art how the circuit of the invention may be connected to employ other types of transistors, for example NPN type transistors.

It will be understood that the invention is not to be limited to the exact construction shown and described, but that various changes and modifications may be made without departing from the spirit and scope of the invention, as defined in the appended claims.

I claim:

1. A transistorized ignition system for an internal combustion engine comprising a plurality of spark plugs, a distributor for distributing electrical energy to said spark plugs, an ignition coil including a primary, a secondary and a feedback winding, said secondary winding being connected to said distributor, a transistor including an emit-ter, a collector and a base, the primary winding of said ignition coil being connected in series with said emitter and said collector, the feedback Winding of said ignition coil being connected between the emitter and the base of said transistor, a control circuit connected to said base for applying a bias to said transistor, a pair of breaker points positioned in said control circuit, said feedback winding applying a pulse of electrical energy to the base of the transistor when said breaker points are opened, the polarity of said pulse being opposite to the polarity of the base bias.

2. A transistorized ignition system for an internal combustion engine comprising, a plurality of spark plugs, a distributor including a rotating arm, said rotating arm being sequentially connected to and disconnected from said spark plugs, an ignition coil including a primary, a secondary and a feedback winding, said secondary winding being connected to said distributor, a transistor including an emitter, a collector and a base, a battery, the primary winding of said ignition coil and the battery being connected in series with said emitter and said collector, a pair of distributor breaker points, a control circuit, said distributor breaker points being positioned in said control circuit, said control circuit applying a bias to the base of said transistor when the breaker points are closed, said breaker points being opened and closed in timed relationship with the rotation of the rotating arm of said distributor, .and being opened when the rotating arm of said distributor is connected to said spark plugs, said feedback winding being connected to supply a pulse of electrical energy to said base when said distributor breaker points are opened, the polarity of said pulse being opposite to the polarity of said bias applied to the base.

3. A transistorized ignition system for an internal combustion engine comprising a plurality of spark plugs, a distributor for distributing electrical energy to said spark plugs, an ignition coil including a primary, a secondary and a feedback winding, said secondary winding being connected to said distributor, a transistor including an emitter, a collector and a base, the primary winding of said ignition coil being connected in series with said emitter and said collector, the feedback winding of said ignition coil being connected between the emitter and the base of said transistor, a control circuit connected to said base for applying a bias to said transistor, a pair of breaker points positioned in said control circuit, said feedback winding applying a pulse of electrical energy to the base of the transistor when said breaker points are opened, the polarity of said pulse being opposite to the polarity of the base bias, and means connected to said emitter and said base for limiting the magnitude of said pulse of electrical energy.

4. A transistorized. ignition system for an internal combustion engine comprising a plurality of spark plugs, a distributor for distributing electrical energy to said spark plugs, an ignition coil including a primary, a secondary and a feedback winding, said secondary winding being connected to said distributor, a transistor including an emitter, a collector and a base, the primary winding of said ignition coil being connected in series with said emitter and said collector, the feedback winding of said ignition coil being connected between the emitter and the base of said transistor, a control circuit connected to said base for applying a bias to said transistor, a pair of breaker points positioned in said control circuit, said feedback winding applying a pulse of electrical energy to the base of the transistor when said breaker points are opened, the polarity of said pulse being opposite to the polarity of the base bias, and a diode connected between said base and said emitter for limiting the magnitude of the potential difference between said emitter and. said base when said pulse of electrical energy is applied.

5. A transistorized ignition system for an internal combustion engine comprising, a plurality of spark plugs, a distributor for distributing electrical energy to said spark plugs, an ignition coil including a primary, a secondary and a feedback winding, said secondary winding being connected in'circuit with said distributor, a transistor having a base, an emitter and a collector, a control circuit including a source of direct current electrical energy connected to said emitter and said base for applying an operating bias to said transistor, said transistor having a load circuit including said source of direct current electrical energy connected to said emitter and collector, the primary winding of said ignition coil being positioned in the load circuit of said transistor, said feedback Winding being connected to said base and said emitter, a pair of breaker points positioned in the control circuit of said transistor, said feedback winding being wound to apply a reverse bias to said transistor when said breaker points are opened.

6. A transistorized ignition system for an internal combustion engine comprising, a plurality of spark plugs, a distributor including a rotating arm, said rotating arm being sequentially connected to and disconnected from said spark plugs, an ignition coil including a primary, a secondary, and a feedback winding, the rotating arm of said distributor and said spark plugs being connected in circuit with the secondary winding of said ignition coil, a transistor including an emitter, a collector and a base, a control circuit including a source of direct current electrical energy, said control circuit connected to said base and said emitter for applying a bias to said transistor, the primary Winding of said ignition coil being connected to one terminal of said source of direct current electrical energy and to the emitter of said transistor, the collector of said transistor being connected to the other terminal of said souce of direct current electrical energy, a pair of breaker points positioned in said control circuit of said transistor, said feedback winding having one terminal connected to the emitter and the other terminal connected to the base of said transistor, said feedback winding applying a pulse of electrical energy to the base of said transistor when said breaker points are opened, said pulse having a polarity opposite to the bias voltage applied for causing said transistor to conduct.

7. A transistorized ignition system for an internal combustion engine comprising, a plurality of spark plugs, a distributor including a rotating arm, said rotating arm being sequentially connected to and disconnected from said spark plugs, an ignition coil including a primary, a secondary, and a feedback Winding, the rotating arm of said distributor and said spark plugs being connected in circuit with the secondary winding of said ignition coil, a transistor including an emitter, a collector and a base, a control circuit including a source of direct current electrical energy, said control circuit connected to said base and said emitter for applying an operating bias to said transistor, the primary winding of said ignition coil being connected to one terminal of said source of direct current electrical energy and to the collector of said transistor, the emitter of said transistor being connected to the other terminal of said source of direct current electrical energy, a pair of breaker points positioned in said control circuit of said transistor, said feedback winding having one terminal connected to the emitter and the other terminal connected to the base of said transistor said feedback winding applying a pulse of electrical energy to the base of said transistor when said breaker points are opened, said pulse having a polarity opposite to the bias applied to the base for causing said transistor to conduct.

8. A transistorized ignition system for an internal combustion engine comprising, a plurality of spark plugs, a distributor for distributing electrical energy to said spark plugs, an ignition coil including a primary and a secondary winding, said secondary winding being connected in circuit with said distributor, a transistor having a base, an emitter and a collector, a control circuit for said transistor including a source of direct current electrical energy, said control circuit connected to said base and said emitter for applying a bias to said transistor, said tran sistor havig a load circuit including said source of direct current electrical energy connected to said emitter and collector, the primary winding of said ignition coil being positioned in the load circuit of said transistor, a pair of breaker points positioned in the control circuit of said transistor, and means for applying a pulse of electrical energy to said base when said breaker points are opened, said pulse of electrical energy having a polarity opposite to the polarity of the bias voltage applied to the base for causing said transistor to conduct, and means connected across said transistor for limiting the potential difference across said transistor.

9. A transistorized ignition system for an internal combustion engine comprising, a plurality of spark plugs, a distributor for distributing electrical energy to said spark plugs, an ignition coil including a primary and a secondary winding, said secondary winding being connected in circuit with said distributor, a transistor having a base, an emitter and a collector, a control circuit including a source of direct current electrical energy for said transistor, said control circuit connected to said base and said emitter for applying a bias to said transistor, said transistor having a load circuit including said source of direct current electrical energy connected to said emitter and collector, the primary Winding of said ignition coil being positioned in the load circuit of said transistor, a pair of breaker points positioned in the control circuit of said transistor, and means for applying a pulse of electrical energy to said base when said breaker points are opened, said pulse of electrical energy having a polarity opposite to the polarity applied to the base for causing said transistor to conduct, and a Zener diode connected across said transistor for limiting the potential difference across said transistor.

10. An ignition system for an internal combustion engine comprising, a plurality of spark plugs, -a distributor for distributing electrical energy to said spark plugs, an ignition coil including a primary and secondary winding, said secondary winding being connected in circuit with said distributor, a transistor having a base, an emitter and a collector, a control circuit including a source of direct current electrical energy for said transistor, said control circuit connected to said base and said emitter for applying a bias to said transistor, said transistor having a load circuit including said source of direct current electrical energy connected to said emitter and collector, the primary Winding of said ignition coil being positioned in the load circuit of said transistor, a pair of breaker points positioned in the control circuit of said transistor, and feedback means coupled to said ignition coil and said base for applying a reverse bias to said transistor when said breaker points are opened.

11. An ignition system for an internal combustion engine comprising, an electrical ignition means, an ignition coil including a primary and a secondary winding, said secondary winding being connected in circuit with said electrical ignition means, a semiconductor device having a control electrode and a pair of output electrodes, a control circuit including a source of direct current electrical energy for said semiconductor device, said control circuit connected to said control electrode and one of said output electrodes for applying an operating bias to said semiconductor device, said semiconductor device having a load circuit including said source of direct current electrical energy connected to said output electrodes, the primary Winding of said ignition coil being positioned in the load circuit of said semiconductor device, a pair of breaker vpoints positioned in the control circuit of said semiconductor device, and feedback means coupled to said ignition coil and said control electrode for applying a reverse bias to said semiconductor device when said breaker points are opened.

12. An ignition system for an internal combustion engine comprising, an electrical ignition means, an ignition coil including a primary and a secondary winding, said secondary Winding being connected in circuit with siad electrical ignition means, a semiconductor device having a control electrode and a pair of output electrodes, a control circuit including a source of direct current electrical energy, said control circuit connected to said control electrode and to one of said output electrodes, said semiconductor device having a load circuit including said source of direct current electrical energy connected to said output electrodes, the primary winding of said ignition coil being positioned in the load circuit of said semiconductor device, means positioned in the control circuit of said semiconductor device and driven in synchronism with said engine for alternately biasing said semiconductor device to conducting and nonconductin-g states, and feedback means coupled to said ignition coil and said control electrode for applying a pulse of electrical energy to said control electrode when said means biases said semiconductor to the nonconducting state of a polarity opposite to the polarity of References Cited by the Examiner UNITED STATES PATENTS 5/1962 Hetzlel' 315-206 X 7/1962 Kerk et a1 315-206 10 JOHN W. HUCKERT, Primary Examiner.

GEORGE WESTBY, Examiner.

R. F. POLISSACK, Assistant Examiner. 

1. A TRANSISTORIZED IGNITION SYSTEM FOR AN INTERNAL COMBUSTION ENGING COMPRISING A PLURALITY OF SPARK PLUGS, A DISTRIBUTOR FOR DISTRIBUTING ELECTRICAL ENERGY TO SAID SPARK PLUGS, AN IGNITION COIL INCLUDING A PRIMARY, A SECONDARY AND A FEEDBACK WINDING, SAID SECONDARY WINDING BEING CONNECTED TO SAID DISTRIBUTOR, A TRANSISTOR INCLUDING AN EMITTER, A COLLECTOR AND A BASE, THE PRIMARY WINDING OF SAID IGNITION COIL BEING CONNECTED IN SERIES WITH SAID EMITTER AND SAID COLLECTOR, THE FEEDBACK WINDING OF SAID IGNITION COIL BEING CONNECTED BETWEEN THE EMITTER AND THE BASE OF SAID TRANSISTOR, A CONTROL CIRCUIT CONNECTED TO SAID BASE FOR APPLYING A BIAS TO SAID TRANSISTOR, A PAIR OF BREAKER POINTS POSITIONED IN SAID CONTROL CIRCUIT, SAID FEEDBACK WINDING APPLYING A PULSE OF ELECTRICAL ENERGY TO THE BASE OF THE TRANSISTOR WHEN SAID BREAKER POINTS ARE OPENED, THE POLARITY OF SAID PULSE BEING OPPOSITE TO THE POLARITY OF THE BASE BIAS. 